Short answer
It depends on whether qurbani was wajib on you. In the Hanafi school a person who owes qurbani must buy another animal if the first dies, is lost or gets a disqualifying defect. A person who did not owe it but bought the animal for qurbani owes nothing more if it dies, and may sacrifice it as it is if it gets a defect.
For someone with the nisab, the duty is on him, not on a particular animal, so a dead, lost or defective animal must be replaced. For someone without the nisab, the animal he bought for qurbani is what became wajib, so his duty ends with that animal.
The four schools agree on this.
Explanation
Hanafi jurists separate two people. The wealthy person owes a qurbani whatever happens to the animal he bought. The poor person owed nothing until he bought an animal with the intention of qurbani; that purchase made that particular animal wajib for him.
- The animal dies or is stolen: wealthy, buy another. Poor, nothing more is owed.
- It breaks a leg or loses an eye before Eid: wealthy, replace it with a sound animal. Poor, he may sacrifice it as it is.
- Injured while being laid down for slaughter: if it struggles and is hurt during the slaughter itself, it still counts for everyone.
- Lost, replaced, then found: wealthy, sacrifice either one. Poor, sacrifice both, since each became wajib on him.
- It gives birth before Eid: sacrifice the young one too, or give it alive to the poor.
- Milk and wool: do not use them before the sacrifice. If you milk it, give the milk in charity.
If you paid a charity and the animal they bought for you died, they should replace it from their own arrangements or refund you so you can arrange another before the days end. For the defects that make an animal unfit, see which animals can be sacrificed. The four schools discuss these cases in detail with differing details; this is the Hanafi rule.
Ask a mufti about your own case. This answer explains the general ruling. When the details of your situation matter, as they do here, ask a qualified mufti and give them the full facts. Where to ask a scholar.
The evidence
Quran, Surah Al-Hajj 22:32
ذَٰلِكَ وَمَن يُعَظِّمْ شَعَٰٓئِرَ ٱللَّهِ فَإِنَّهَا مِن تَقْوَى ٱلْقُلُوبِ ﴿٣٢﴾
That [is so]. And whoever honors the symbols of Allah - indeed, it is from the piety of hearts.
Taking care of the sacrificial animal is part of honouring Allah's symbols.
Quran, Surah Al-Hajj 22:36
وَٱلْبُدْنَ جَعَلْنَٰهَا لَكُم مِّن شَعَٰٓئِرِ ٱللَّهِ لَكُمْ فِيهَا خَيْرٌۭ ۖ فَٱذْكُرُوا۟ ٱسْمَ ٱللَّهِ عَلَيْهَا صَوَآفَّ ۖ فَإِذَا وَجَبَتْ جُنُوبُهَا فَكُلُوا۟ مِنْهَا وَأَطْعِمُوا۟ ٱلْقَانِعَ وَٱلْمُعْتَرَّ ۚ كَذَٰلِكَ سَخَّرْنَٰهَا لَكُمْ لَعَلَّكُمْ تَشْكُرُونَ ﴿٣٦﴾
And the camels and cattle We have appointed for you as among the symbols of Allah; for you therein is good. So mention the name of Allah upon them when lined up [for sacrifice]; and when they are [lifeless] on their sides, then eat from them and feed the needy and the beggar. Thus have We subjected them to you that you may be grateful.
The sacrificial animals are among the symbols of Allah.
Where the ruling is recorded
- al-Hidaya, Kitab al-Udhiyah. The difference between the rich and the poor when the animal dies or becomes defective.
- al-Fatawa al-Hindiyya, Kitab al-Udhiyah, chapter on defects. A defect caused during the act of slaughter does not matter; lost and found animals.
- Bada'i al-Sana'i, Kitab al-Tadhiyah. Using the milk and wool of the qurbani animal and its young.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.